1. Technical Field of the Invention
The present invention relates to oscillator circuitry, and particularly to circuitry for controlling current dissipated by crystal oscillator circuits.
2. Description of the Related Art
Crystal oscillators have been used in the electronics industry for decades for providing a clock or other signal having a fixed, predetermined frequency. For certain applications, some existing crystal oscillator circuits operate at relatively low voltage and low current levels. However, these low voltage, low current oscillator circuits take an appreciably long time to start up and stabilize. Oscillator circuits having a relatively prolonged time to start-up and stabilize adversely affect normal system operation as well as testing of the circuitry associated with the oscillator circuits.
At least one existing oscillator circuit design allows for higher current dissipation by the oscillator when initially started, and thereafter switches the oscillator current to a lower current level. This existing oscillator circuit utilizes an amplitude detector to detect current level consumed by the oscillator circuit and to provide feedback to the current source providing current to the oscillator circuit based upon the current detected. A problem with this existing oscillator circuit, however, is that it results in a rather complex circuit design. What is needed, then, is an oscillator circuit that quickly starts and stabilizes with little overhead.